Neuromedin U is a peptide isolated and purified from porcine spinal cords, based on its activity to contract smooth-muscle in rat uterus. Two neuromedins U, namely, neuromedin U-8 composed of 8 amino acid residues and neuromedin U-25 composed of 25 amino acid residues are first reported (Minamino, N. et al., Biochem. Biophys. Res. Commun., 130, 1078-1085, 1985). The sequence of neuromedin U-8 is identical to the C-terminal sequence of neuromedin U-25 and the upstream region contains a basic amino acid pair often observed in the cleavage site for processing, and the two neuromedins U are thus expected to be derived from a common precursor. Also, other physiological functions besides the smooth muscle contraction activity are widely known. Such functions reportedly include, for example, an increase in blood pressure (Minamino. N. et al.), a decrease in splanchnic blood flow (Sumi, S. et al., Life Sci., 41, 1585-1590, 1987), adjustment of ion transportation in intestine (Brown, D. R. and Quito, F. L., Eur. J. Pharmacol. 155, 159-162, 1998) and an increase in ACTH and a subsequent increase in corticosterone after subcutaneous administration of neuromedin U (Malendowicz, L. K. et al., In Vivo, 7, 419-422, 1993). Furthermore, TGR1 (WO 01/57524) and FM-3 (WO 00/02918) are hitherto reported as receptors for neuromedin U.